blog_web/assets/js/141.8726d4cf.js

(window.webpackJsonp=window.webpackJsonp||[]).push([[141],{470:function(t,s,a){"use strict";a.r(s);var n=a(3),e=Object(n.a)({},(function(){var t=this,s=t._self._c;return s("ContentSlotsDistributor",{attrs:{"slot-key":t.$parent.slotKey}},[s("h1",{attrs:{id:"事件"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#事件"}},[t._v("#")]),t._v(" 事件")]),t._v(" "),s("h2",{attrs:{id:"一、eventtarget-接口"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#一、eventtarget-接口"}},[t._v("#")]),t._v(" 一、EventTarget 接口")]),t._v(" "),s("p",[t._v("事件的本质是程序各个组成部分之间的一种通信方式，也是异步编程的一种实现。DOM 支持大量的事件，本章开始介绍 "),s("strong",[t._v("DOM 的事件编程")]),t._v("。")]),t._v(" "),s("h3",{attrs:{id:"_1、概述"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_1、概述"}},[t._v("#")]),t._v(" 1、概述")]),t._v(" "),s("p",[s("strong",[t._v("DOM 的事件操作（监听和触发），都定义在"),s("code",[t._v("EventTarget")]),t._v("接口")]),t._v("。所有节点对象都部署了这个接口，其他一些需要事件通信的浏览器内置对象（比如，"),s("code",[t._v("XMLHttpRequest")]),t._v("、"),s("code",[t._v("AudioNode")]),t._v("、"),s("code",[t._v("AudioContext")]),t._v("）也部署了这个接口。")]),t._v(" "),s("p",[t._v("该接口主要提供三个实例方法。")]),t._v(" "),s("ul",[s("li",[s("code",[t._v("addEventListener")]),t._v("：绑定事件的监听函数")]),t._v(" "),s("li",[s("code",[t._v("removeEventListener")]),t._v("：移除事件的监听函数")]),t._v(" "),s("li",[s("code",[t._v("dispatchEvent")]),t._v("：触发事件")])]),t._v(" "),s("h3",{attrs:{id:"_2、eventtarget-addeventlistener"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_2、eventtarget-addeventlistener"}},[t._v("#")]),t._v(" 2、EventTarget.addEventListener()")]),t._v(" "),s("p",[s("code",[t._v("EventTarget.addEventListener()")]),t._v("用于"),s("strong",[t._v("在当前节点或对象上，定义一个特定事件的监听函数")]),t._v("。"),s("strong",[t._v("一旦这个事件发生，就会执行监听函数")]),t._v("。该方法没有返回值。")]),t._v(" "),s("div",{staticClass:"language-js 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"),s("div",{staticClass:"line-numbers-wrapper"},[s("span",{staticClass:"line-number"},[t._v("1")]),s("br"),s("span",{staticClass:"line-number"},[t._v("2")]),s("br"),s("span",{staticClass:"line-number"},[t._v("3")]),s("br"),s("span",{staticClass:"line-number"},[t._v("4")]),s("br"),s("span",{staticClass:"line-number"},[t._v("5")]),s("br"),s("span",{staticClass:"line-number"},[t._v("6")]),s("br")])]),s("p",[t._v("上面代码中，"),s("code",[t._v("button")]),t._v("节点的"),s("code",[t._v("addEventListener")]),t._v("方法绑定"),s("code",[t._v("click")]),t._v("事件的监听函数"),s("code",[t._v("hello")]),t._v("，该函数只在冒泡阶段触发。")]),t._v(" "),s("p",[t._v("关于参数，有两个地方需要注意。")]),t._v(" "),s("p",[t._v("首先，第二个参数除了监听函数，还可以是一个具有"),s("code",[t._v("handleEvent")]),t._v("方法的对象。")]),t._v(" "),s("div",{staticClass:"language-js line-numbers-mode"},[s("pre",{pre:!0,attrs:{class:"language-js"}},[s("code",[t._v("buttonElement"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token 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"),s("p",[t._v("如果希望事件监听函数"),s("strong",[t._v("只执行一次")]),t._v("，可以打开属性配置对象的"),s("code",[t._v("once")]),t._v("属性。")]),t._v(" "),s("div",{staticClass:"language-js line-numbers-mode"},[s("pre",{pre:!0,attrs:{class:"language-js"}},[s("code",[t._v("element"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("addEventListener")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v("'click'")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("function")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token parameter"}},[t._v("event")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n  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EventPhase: 'bubble' 冒泡阶段")]),t._v("\n")])]),t._v(" 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"),s("p",[s("strong",[t._v("注意")]),t._v("，"),s("strong",[t._v("浏览器总是假定"),s("code",[t._v("click")]),t._v("事件的目标节点，就是点击位置嵌套最深的那个节点")]),t._v("（本例是"),s("code",[t._v("<div>")]),t._v("节点里面的"),s("code",[t._v("<p>")]),t._v("节点）。所以，"),s("strong",[s("code",[t._v("<p>")]),t._v("节点的捕获阶段和冒泡阶段，都会显示为"),s("code",[t._v("target")]),t._v("阶段。")])]),t._v(" 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--\x3e body --\x3e html --\x3e document(文档对象) --\x3e window(浏览器对象)\n")])]),t._v(" "),s("div",{staticClass:"line-numbers-wrapper"},[s("span",{staticClass:"line-number"},[t._v("1")]),s("br"),s("span",{staticClass:"line-number"},[t._v("2")]),s("br"),s("span",{staticClass:"line-number"},[t._v("3")]),s("br"),s("span",{staticClass:"line-number"},[t._v("4")]),s("br"),s("span",{staticClass:"line-number"},[t._v("5")]),s("br")])]),s("h3",{attrs:{id:"_4、事件的代理"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_4、事件的代理"}},[t._v("#")]),t._v(" 4、事件的代理")]),t._v(" "),s("p",[t._v("由于事件会在冒泡阶段向上传播到父节点，因此可以把"),s("strong",[t._v("子节点的监听函数定义在父节点上，由父节点的监听函数统一处理多个子元素的事件。这种方法叫做事件的代理")]),t._v("（delegation）。")]),t._v(" "),s("div",{staticClass:"language-js line-numbers-mode"},[s("pre",{pre:!0,attrs:{class:"language-js"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("var")]),t._v(" ul "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" document"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("querySelector")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v("'ul'")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\nul"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("addEventListener")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v("'click'")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("function")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token 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"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// 浏览器假定click嵌套最深的元素是目标元素")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// some code")]),t._v("\n  "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n")])]),t._v(" "),s("div",{staticClass:"line-numbers-wrapper"},[s("span",{staticClass:"line-number"},[t._v("1")]),s("br"),s("span",{staticClass:"line-number"},[t._v("2")]),s("br"),s("span",{staticClass:"line-number"},[t._v("3")]),s("br"),s("span",{staticClass:"line-number"},[t._v("4")]),s("br"),s("span",{staticClass:"line-number"},[t._v("5")]),s("br"),s("span",{staticClass:"line-number"},[t._v("6")]),s("br"),s("span",{staticClass:"line-number"},[t._v("7")]),s("br")])]),s("p",[t._v("上面代码中，"),s("code",[t._v("click")]),t._v("事件的监听函数定义在"),s("code",[t._v("<ul>")]),t._v("节点，但是实际上，它处理的是子节点"),s("code",[t._v("<li>")]),t._v("的"),s("code",[t._v("click")]),t._v("事件。这样做的好处是，只要定义一个监听函数，就能处理多个子节点的事件，而不用在每个"),s("code",[t._v("<li>")]),t._v("节点上定义监听函数。而且以后再添加子节点，监听函数依然有效。")]),t._v(" "),s("h5",{attrs:{id:"阻止事件冒泡-event-stoppropagation"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#阻止事件冒泡-event-stoppropagation"}},[t._v("#")]),t._v(" 阻止事件冒泡 event.stopPropagation()")]),t._v(" "),s("p",[t._v("如果希望事件到某个节点为止，不再传播，可以使用事件对象的"),s("code",[t._v("stopPropagation")]),t._v("方法。")]),t._v(" "),s("div",{staticClass:"language-js line-numbers-mode"},[s("pre",{pre:!0,attrs:{class:"language-js"}},[s("code",[s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// 事件传播到 p 元素后，就不再向下传播了")]),t._v("\np"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("addEventListener")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v("'click'")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("function")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token parameter"}},[t._v("event")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n  event"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stopPropagation")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// 该方法在事件对象event上")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token boolean"}},[t._v("true")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// true表示在捕获阶段绑定事件监听函数")]),t._v("\n\n"),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// 事件冒泡到 p 元素后，就不再向上冒泡了")]),t._v("\np"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("addEventListener")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v("'click'")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("function")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token parameter"}},[t._v("event")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n  event"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stopPropagation")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token boolean"}},[t._v("false")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// false表示在冒泡阶段（默认值）绑定事件监听函数")]),t._v("\n")])]),t._v(" "),s("div",{staticClass:"line-numbers-wrapper"},[s("span",{staticClass:"line-number"},[t._v("1")]),s("br"),s("span",{staticClass:"line-number"},[t._v("2")]),s("br"),s("span",{staticClass:"line-number"},[t._v("3")]),s("br"),s("span",{staticClass:"line-number"},[t._v("4")]),s("br"),s("span",{staticClass:"line-number"},[t._v("5")]),s("br"),s("span",{staticClass:"line-number"},[t._v("6")]),s("br"),s("span",{staticClass:"line-number"},[t._v("7")]),s("br"),s("span",{staticClass:"line-number"},[t._v("8")]),s("br"),s("span",{staticClass:"line-number"},[t._v("9")]),s("br")])]),s("p",[t._v("上面代码中，"),s("code",[t._v("stopPropagation")]),t._v("方法分别在捕获阶段和冒泡阶段，阻止了事件的传播。")]),t._v(" "),s("p",[t._v("但是，"),s("strong",[s("code",[t._v("stopPropagation")]),t._v("方法只会阻止事件的传播，不会阻止该事件触发"),s("code",[t._v("<p>")]),t._v("节点的其他"),s("code",[t._v("click")]),t._v("事件的监听函数")]),t._v("。也就是说，不是彻底取消"),s("code",[t._v("click")]),t._v("事件。")]),t._v(" "),s("div",{staticClass:"language-js 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"),s("div",{staticClass:"line-numbers-wrapper"},[s("span",{staticClass:"line-number"},[t._v("1")]),s("br"),s("span",{staticClass:"line-number"},[t._v("2")]),s("br"),s("span",{staticClass:"line-number"},[t._v("3")]),s("br"),s("span",{staticClass:"line-number"},[t._v("4")]),s("br"),s("span",{staticClass:"line-number"},[t._v("5")]),s("br"),s("span",{staticClass:"line-number"},[t._v("6")]),s("br"),s("span",{staticClass:"line-number"},[t._v("7")]),s("br"),s("span",{staticClass:"line-number"},[t._v("8")]),s("br"),s("span",{staticClass:"line-number"},[t._v("9")]),s("br")])]),s("p",[t._v("上面代码中，"),s("code",[t._v("stopImmediatePropagation")]),t._v("方法可以彻底取消这个事件，使得后面绑定的所有"),s("code",[t._v("click")]),t._v("监听函数都不再触发。所以，只会输出1，不会输出2。")]),t._v(" "),s("h2",{attrs:{id:"三、event-对象"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#三、event-对象"}},[t._v("#")]),t._v(" 三、Event 对象")]),t._v(" "),s("h3",{attrs:{id:"_1-概述"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_1-概述"}},[t._v("#")]),t._v(" 1. 概述")]),t._v(" "),s("p",[s("strong",[t._v("事件发生以后，会产生一个事件对象，作为参数传给监听函数")]),t._v("。浏览器原生提供一个"),s("code",[t._v("Event")]),t._v("对象，所有的事件都是这个对象的实例，或者说继承了"),s("code",[t._v("Event.prototype")]),t._v("对象。")]),t._v(" "),s("p",[s("strong",[s("code",[t._v("Event")]),t._v("对象本身就是一个构造函数，可以用来生成新的实例")]),t._v("。")]),t._v(" "),s("div",{staticClass:"language-js line-numbers-mode"},[s("pre",{pre:!0,attrs:{class:"language-js"}},[s("code",[t._v("event "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Event")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("type"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" options"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// 参数一，事件名称； 参数二，事件对象的配置对象")]),t._v("\n")])]),t._v(" "),s("div",{staticClass:"line-numbers-wrapper"},[s("span",{staticClass:"line-number"},[t._v("1")]),s("br")])]),s("p",[s("code",[t._v("Event")]),t._v("构造函数接受两个参数。第一个参数"),s("code",[t._v("type")]),t._v("是字符串，表示事件的名称；第二个参数"),s("code",[t._v("options")]),t._v("是一个对象，表示事件对象的配置。该对象主要有下面两个属性。")]),t._v(" "),s("ul",[s("li",[s("code",[t._v("bubbles")]),t._v("：布尔值，可选，默认为"),s("code",[t._v("false")]),t._v("，表示事件对象"),s("strong",[t._v("是否冒泡")]),t._v("。")]),t._v(" "),s("li",[s("code",[t._v("cancelable")]),t._v("：布尔值，可选，默认为"),s("code",[t._v("false")]),t._v("，表示事件"),s("strong",[t._v("是否可以被取消")]),t._v("，即能否用"),s("code",[t._v("Event.preventDefault()")]),t._v("取消这个事件。一旦事件被取消，就好像从来没有发生过，不会触发浏览器对该事件的默认行为。")])]),t._v(" "),s("div",{staticClass:"language-js line-numbers-mode"},[s("pre",{pre:!0,attrs:{class:"language-js"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("var")]),t._v(" ev "),s("span",{pre:!0,attrs:{class:"token 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document"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("querySelector")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v("'p'")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("function")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("callback")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token parameter"}},[t._v("event")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n  "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("var")]),t._v(" tag "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" event"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("currentTarget"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("tagName"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n  console"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("log")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v("'Tag: '")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("+")]),t._v(" tag"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// 没有任何输出")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\ndiv"),s("span",{pre:!0,attrs:{class:"token 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class-name"}},[t._v("Event")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v("'click'")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\np"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("dispatchEvent")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("click"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// 给p发出一个click事件，该事件默认不会冒泡，因此不会触发父元素div的click事件")]),t._v("\n")])]),t._v(" "),s("div",{staticClass:"line-numbers-wrapper"},[s("span",{staticClass:"line-number"},[t._v("1")]),s("br"),s("span",{staticClass:"line-number"},[t._v("2")]),s("br"),s("span",{staticClass:"line-number"},[t._v("3")]),s("br"),s("span",{staticClass:"line-number"},[t._v("4")]),s("br"),s("span",{staticClass:"line-number"},[t._v("5")]),s("br"),s("span",{staticClass:"line-number"},[t._v("6")]),s("br"),s("span",{staticClass:"line-number"},[t._v("7")]),s("br"),s("span",{staticClass:"line-number"},[t._v("8")]),s("br"),s("span",{staticClass:"line-number"},[t._v("9")]),s("br"),s("span",{staticClass:"line-number"},[t._v("10")]),s("br"),s("span",{staticClass:"line-number"},[t._v("11")]),s("br"),s("span",{staticClass:"line-number"},[t._v("12")]),s("br"),s("span",{staticClass:"line-number"},[t._v("13")]),s("br"),s("span",{staticClass:"line-number"},[t._v("14")]),s("br")])]),s("p",[t._v("上面代码中，"),s("code",[t._v("p")]),t._v("元素发出一个"),s("code",[t._v("click")]),t._v("事件，该事件默认不会冒泡。"),s("code",[t._v("div.addEventListener")]),t._v("方法指定在冒泡阶段监听，因此监听函数不会触发。如果写成"),s("code",[t._v("div.addEventListener('click', 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"),s("h3",{attrs:{id:"_2-实例属性"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_2-实例属性"}},[t._v("#")]),t._v(" 2. 实例属性")]),t._v(" "),s("h4",{attrs:{id:"_2-1-event-bubbles-是否会冒泡-只读-event-eventphase-返回整数-表示事件所处阶段-只读"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_2-1-event-bubbles-是否会冒泡-只读-event-eventphase-返回整数-表示事件所处阶段-只读"}},[t._v("#")]),t._v(" 2.1 Event.bubbles 是否会冒泡，只读，Event.eventPhase 返回整数，表示事件所处阶段，只读")]),t._v(" "),s("p",[s("code",[t._v("Event.bubbles")]),t._v("属性"),s("strong",[t._v("返回一个布尔值，表示当前事件是否会冒泡")]),t._v("。该属性为"),s("strong",[t._v("只读")]),t._v("属性，一般用来了解 Event 实例是否可以冒泡。前面说过，除非显式声明，"),s("code",[t._v("Event")]),t._v("构造函数生成的事件，默认是不冒泡的。")]),t._v(" "),s("p",[s("code",[t._v("Event.eventPhase")]),t._v("属性"),s("strong",[t._v("返回一个整数常量，表示事件目前所处的阶段。该属性只读")]),t._v("。")]),t._v(" "),s("div",{staticClass:"language-js line-numbers-mode"},[s("pre",{pre:!0,attrs:{class:"language-js"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("var")]),t._v(" phase "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" event"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("eventPhase"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n")])]),t._v(" "),s("div",{staticClass:"line-numbers-wrapper"},[s("span",{staticClass:"line-number"},[t._v("1")]),s("br")])]),s("p",[s("code",[t._v("Event.eventPhase")]),t._v("的返回值有四种可能。")]),t._v(" "),s("ul",[s("li",[t._v("0，事件目前"),s("strong",[t._v("没有发生")]),t._v("。")]),t._v(" "),s("li",[t._v("1，事件目前处于"),s("strong",[t._v("捕获阶段")]),t._v("，即处于从祖先节点向目标节点的传播过程中。")]),t._v(" "),s("li",[t._v("2，事件"),s("strong",[t._v("到达目标节点")]),t._v("，即"),s("code",[t._v("Event.target")]),t._v("属性指向的那个节点。")]),t._v(" "),s("li",[t._v("3，事件处于"),s("strong",[t._v("冒泡阶段")]),t._v("，即处于从目标节点向祖先节点的反向传播过程中。")])]),t._v(" "),s("h4",{attrs:{id:"_2-2-event-cancelable-是否可取消默认行为-event-cancelbubble是否阻止冒泡-event-defaultprevented-是否调用过取消默认行为方法"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_2-2-event-cancelable-是否可取消默认行为-event-cancelbubble是否阻止冒泡-event-defaultprevented-是否调用过取消默认行为方法"}},[t._v("#")]),t._v(" 2.2 Event.cancelable 是否可取消默认行为，Event.cancelBubble是否阻止冒泡，event.defaultPrevented 是否调用过取消默认行为方法")]),t._v(" "),s("p",[s("code",[t._v("Event.cancelable")]),t._v("属性"),s("strong",[t._v("返回一个布尔值，表示事件是否可以取消")]),t._v("。该属性为"),s("strong",[t._v("只读")]),t._v("属性，一般用来了解 Event 实例的特性。")]),t._v(" "),s("p",[s("strong",[t._v("大多数浏览器的原生事件是可以取消的")]),t._v("。比如，取消"),s("code",[t._v("click")]),t._v("事件，点击链接将无效。但是除非显式声明，"),s("code",[t._v("Event")]),t._v("构造函数生成的事件，"),s("strong",[t._v("默认是不可以取消的")]),t._v("。")]),t._v(" "),s("div",{staticClass:"language-js line-numbers-mode"},[s("pre",{pre:!0,attrs:{class:"language-js"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("var")]),t._v(" evt 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"),s("div",{staticClass:"line-numbers-wrapper"},[s("span",{staticClass:"line-number"},[t._v("1")]),s("br"),s("span",{staticClass:"line-number"},[t._v("2")]),s("br")])]),s("p",[t._v("当"),s("code",[t._v("Event.cancelable")]),t._v("属性为"),s("code",[t._v("true")]),t._v("时，调用"),s("code",[t._v("Event.preventDefault()")]),t._v("就可以取消这个事件，阻止浏览器对该事件的默认行为。")]),t._v(" "),s("p",[t._v("如果事件不能取消，调用"),s("code",[t._v("Event.preventDefault()")]),t._v("会没有任何效果。所以使用这个方法之前，最好用"),s("code",[t._v("Event.cancelable")]),t._v("属性判断一下是否可以取消。")]),t._v(" "),s("div",{staticClass:"language-js line-numbers-mode"},[s("pre",{pre:!0,attrs:{class:"language-js"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("function")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("preventEvent")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token parameter"}},[t._v("event")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n  "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("if")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("event"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("cancelable"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n    event"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("preventDefault")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n  "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("else")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n    console"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("warn")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v("'This event couldn\\'t be canceled.'")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n    console"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("dir")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("event"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n  "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token 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"),s("div",{staticClass:"line-numbers-wrapper"},[s("span",{staticClass:"line-number"},[t._v("1")]),s("br"),s("span",{staticClass:"line-number"},[t._v("2")]),s("br"),s("span",{staticClass:"line-number"},[t._v("3")]),s("br")])]),s("h4",{attrs:{id:"_2-3-event-currenttarget当前正在通过的节点-event-target目标节点"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_2-3-event-currenttarget当前正在通过的节点-event-target目标节点"}},[t._v("#")]),t._v(" 2.3 Event.currentTarget当前正在通过的节点，Event.target目标节点")]),t._v(" "),s("p",[t._v("事件发生以后，会经过捕获和冒泡两个阶段，依次通过多个 DOM 节点。因此，任意时点都有两个与事件相关的节点，一个是事件的"),s("strong",[t._v("原始触发节点")]),t._v("（"),s("code",[t._v("Event.target")]),t._v("），另一个是事件"),s("strong",[t._v("当前正在通过的节点")]),t._v("（"),s("code",[t._v("Event.currentTarget")]),t._v("）。"),s("strong",[t._v("前者通常是后者的后代节点")]),t._v("。")]),t._v(" "),s("p",[s("code",[t._v("Event.currentTarget")]),t._v("属性返回事件"),s("strong",[t._v("当前所在的节点")]),t._v("，即事件当前正在通过的节点，也就是当前正在执行的监听函数所在的那个节点。"),s("strong",[t._v("随着事件的传播，这个属性的值会变")]),t._v("。")]),t._v(" "),s("p",[s("code",[t._v("Event.target")]),t._v("属性返回"),s("strong",[t._v("原始触发事件的那个节点")]),t._v("，即事件最初发生的节点。这个属性不会随着事件的传播而改变。")]),t._v(" "),s("p",[t._v("事件传播过程中，不同节点的监听函数内部的"),s("code",[t._v("Event.target")]),t._v("与"),s("code",[t._v("Event.currentTarget")]),t._v("属性的值是不一样的。")]),t._v(" "),s("div",{staticClass:"language-js line-numbers-mode"},[s("pre",{pre:!0,attrs:{class:"language-js"}},[s("code",[s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// HTML 代码为")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v('// <p id="para">Hello <em>World</em></p>')]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("function")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("hide")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token parameter"}},[t._v("e")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token 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"),s("div",{staticClass:"line-numbers-wrapper"},[s("span",{staticClass:"line-number"},[t._v("1")]),s("br"),s("span",{staticClass:"line-number"},[t._v("2")]),s("br"),s("span",{staticClass:"line-number"},[t._v("3")]),s("br"),s("span",{staticClass:"line-number"},[t._v("4")]),s("br"),s("span",{staticClass:"line-number"},[t._v("5")]),s("br"),s("span",{staticClass:"line-number"},[t._v("6")]),s("br"),s("span",{staticClass:"line-number"},[t._v("7")]),s("br"),s("span",{staticClass:"line-number"},[t._v("8")]),s("br"),s("span",{staticClass:"line-number"},[t._v("9")]),s("br"),s("span",{staticClass:"line-number"},[t._v("10")]),s("br"),s("span",{staticClass:"line-number"},[t._v("11")]),s("br"),s("span",{staticClass:"line-number"},[t._v("12")]),s("br")])]),s("p",[t._v("上面代码中，"),s("code",[t._v("<em>")]),t._v("是"),s("code",[t._v("<p>")]),t._v("的子节点，点击"),s("code",[t._v("<em>")]),t._v("或者点击"),s("code",[t._v("<p>")]),t._v("，都会导致监听函数执行。这时，"),s("code",[t._v("e.target")]),t._v("总是指向原始点击位置的那个节点，而"),s("code",[t._v("e.currentTarget")]),t._v("指向事件传播过程中正在经过的那个节点。由于监听函数只有事件经过时才会触发，所以"),s("code",[t._v("e.currentTarget")]),t._v("总是等同于监听函数内部的"),s("code",[t._v("this")]),t._v("。")]),t._v(" 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"),s("div",{staticClass:"line-numbers-wrapper"},[s("span",{staticClass:"line-number"},[t._v("1")]),s("br"),s("span",{staticClass:"line-number"},[t._v("2")]),s("br"),s("span",{staticClass:"line-number"},[t._v("3")]),s("br"),s("span",{staticClass:"line-number"},[t._v("4")]),s("br"),s("span",{staticClass:"line-number"},[t._v("5")]),s("br"),s("span",{staticClass:"line-number"},[t._v("6")]),s("br"),s("span",{staticClass:"line-number"},[t._v("7")]),s("br"),s("span",{staticClass:"line-number"},[t._v("8")]),s("br"),s("span",{staticClass:"line-number"},[t._v("9")]),s("br"),s("span",{staticClass:"line-number"},[t._v("10")]),s("br"),s("span",{staticClass:"line-number"},[t._v("11")]),s("br"),s("span",{staticClass:"line-number"},[t._v("12")]),s("br"),s("span",{staticClass:"line-number"},[t._v("13")]),s("br"),s("span",{staticClass:"line-number"},[t._v("14")]),s("br"),s("span",{staticClass:"line-number"},[t._v("15")]),s("br"),s("span",{staticClass:"line-number"},[t._v("16")]),s("br"),s("span",{staticClass:"line-number"},[t._v("17")]),s("br"),s("span",{staticClass:"line-number"},[t._v("18")]),s("br"),s("span",{staticClass:"line-number"},[t._v("19")]),s("br"),s("span",{staticClass:"line-number"},[t._v("20")]),s("br"),s("span",{staticClass:"line-number"},[t._v("21")]),s("br"),s("span",{staticClass:"line-number"},[t._v("22")]),s("br")])]),s("h4",{attrs:{id:"_2-6-event-istrusted-是否由真实用户行为产生的事件"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_2-6-event-istrusted-是否由真实用户行为产生的事件"}},[t._v("#")]),t._v(" 2.6 Event.isTrusted 是否由真实用户行为产生的事件")]),t._v(" "),s("p",[s("code",[t._v("Event.isTrusted")]),t._v("属性返回一个"),s("strong",[t._v("布尔值")]),t._v("，表示"),s("strong",[t._v("该事件是否由真实的用户行为产生")]),t._v("。比如，用户点击链接会产生一个"),s("code",[t._v("click")]),t._v("事件，该事件是用户产生的；"),s("code",[t._v("Event")]),t._v("构造函数生成的事件，则是脚本产生的。")]),t._v(" "),s("div",{staticClass:"language-js line-numbers-mode"},[s("pre",{pre:!0,attrs:{class:"language-js"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("var")]),t._v(" evt "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Event")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v("'foo'")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\nevt"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("isTrusted "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// false")]),t._v("\n")])]),t._v(" "),s("div",{staticClass:"line-numbers-wrapper"},[s("span",{staticClass:"line-number"},[t._v("1")]),s("br"),s("span",{staticClass:"line-number"},[t._v("2")]),s("br")])]),s("p",[t._v("上面代码中，"),s("code",[t._v("evt")]),t._v("对象是脚本产生的，所以"),s("code",[t._v("isTrusted")]),t._v("属性返回"),s("code",[t._v("false")]),t._v("。")]),t._v(" "),s("h4",{attrs:{id:"_2-7-event-detail-事件的细节-单击or双击等"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_2-7-event-detail-事件的细节-单击or双击等"}},[t._v("#")]),t._v(" 2.7 Event.detail 事件的细节（单击or双击等）")]),t._v(" "),s("p",[s("code",[t._v("Event.detail")]),t._v("属性只有浏览器的 UI （用户界面）事件才具有。该属性返回一个数值，表示事件的某种信息。具体含义与事件类型相关。比如，对于"),s("code",[t._v("click")]),t._v("和"),s("code",[t._v("dblclick")]),t._v("事件，"),s("code",[t._v("Event.detail")]),t._v("是鼠标按下的次数（"),s("code",[t._v("1")]),t._v("表示单击，"),s("code",[t._v("2")]),t._v("表示双击，"),s("code",[t._v("3")]),t._v("表示三击）；对于鼠标滚轮事件，"),s("code",[t._v("Event.detail")]),t._v("是滚轮正向滚动的距离，负值就是负向滚动的距离，返回值总是3的倍数。")]),t._v(" "),s("div",{staticClass:"language-js line-numbers-mode"},[s("pre",{pre:!0,attrs:{class:"language-js"}},[s("code",[s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// HTML 代码如下")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// <p>Hello</p>")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("function")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("giveDetails")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token parameter"}},[t._v("e")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n  console"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("log")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("e"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("detail"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// 快速点击的次数")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\ndocument"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("querySelector")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v("'p'")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("onclick "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" giveDetails"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n")])]),t._v(" "),s("div",{staticClass:"line-numbers-wrapper"},[s("span",{staticClass:"line-number"},[t._v("1")]),s("br"),s("span",{staticClass:"line-number"},[t._v("2")]),s("br"),s("span",{staticClass:"line-number"},[t._v("3")]),s("br"),s("span",{staticClass:"line-number"},[t._v("4")]),s("br"),s("span",{staticClass:"line-number"},[t._v("5")]),s("br"),s("span",{staticClass:"line-number"},[t._v("6")]),s("br"),s("span",{staticClass:"line-number"},[t._v("7")]),s("br")])]),s("h3",{attrs:{id:"_3、实例方法"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_3、实例方法"}},[t._v("#")]),t._v(" 3、实例方法")]),t._v(" "),s("h4",{attrs:{id:"_3-1-event-preventdefault-取消浏览器对当前事件的默认行为"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_3-1-event-preventdefault-取消浏览器对当前事件的默认行为"}},[t._v("#")]),t._v(" 3.1 Event.preventDefault()  取消浏览器对当前事件的默认行为")]),t._v(" "),s("p",[s("code",[t._v("Event.preventDefault")]),t._v("方法"),s("strong",[t._v("取消浏览器对当前事件的默认行为")]),t._v("。比如点击链接后，浏览器默认会跳转到另一个页面，使用这个方法以后，就不会跳转了；再比如，按一下空格键，页面向下滚动一段距离，使用这个方法以后也不会滚动了。该方法生效的前提是，事件对象的"),s("code",[t._v("cancelable")]),t._v("属性为"),s("code",[t._v("true")]),t._v("，如果为"),s("code",[t._v("false")]),t._v("，调用该方法没有任何效果。")]),t._v(" "),s("p",[s("strong",[t._v("注意，该方法只是取消事件对当前元素的默认影响，不会阻止事件的传播")]),t._v("。如果要阻止传播，可以使用"),s("code",[t._v("stopPropagation()")]),t._v("或"),s("code",[t._v("stopImmediatePropagation()")]),t._v("方法。")]),t._v(" "),s("div",{staticClass:"language-js line-numbers-mode"},[s("pre",{pre:!0,attrs:{class:"language-js"}},[s("code",[s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// HTML 代码为")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v('// <input type="checkbox" id="my-checkbox" />')]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("var")]),t._v(" cb "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" document"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("getElementById")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v("'my-checkbox'")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\ncb"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("addEventListener")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("\n  "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v("'click'")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v("\n  "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("function")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token parameter"}},[t._v("e")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v(" e"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("preventDefault")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v("\n  "),s("span",{pre:!0,attrs:{class:"token boolean"}},[t._v("false")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n")])]),t._v(" "),s("div",{staticClass:"line-numbers-wrapper"},[s("span",{staticClass:"line-number"},[t._v("1")]),s("br"),s("span",{staticClass:"line-number"},[t._v("2")]),s("br"),s("span",{staticClass:"line-number"},[t._v("3")]),s("br"),s("span",{staticClass:"line-number"},[t._v("4")]),s("br"),s("span",{staticClass:"line-number"},[t._v("5")]),s("br"),s("span",{staticClass:"line-number"},[t._v("6")]),s("br"),s("span",{staticClass:"line-number"},[t._v("7")]),s("br"),s("span",{staticClass:"line-number"},[t._v("8")]),s("br"),s("span",{staticClass:"line-number"},[t._v("9")]),s("br")])]),s("p",[t._v("上面代码中，浏览器的默认行为是单击会选中单选框，取消这个行为，就导致无法选中单选框。")]),t._v(" "),s("p",[t._v("利用这个方法，可以为文本输入框设置校验条件。如果用户的输入不符合条件，就无法将字符输入文本框。")]),t._v(" "),s("h6",{attrs:{id:"例子-只能输入字母的输入框"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#例子-只能输入字母的输入框"}},[t._v("#")]),t._v(" 例子：只能输入字母的输入框")]),t._v(" "),s("div",{staticClass:"language-js line-numbers-mode"},[s("pre",{pre:!0,attrs:{class:"language-js"}},[s("code",[s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// HTML 代码为")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v('// <input type="text" id="my-input" />')]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("var")]),t._v(" input "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" document"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("getElementById")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v("'my-input'")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\ninput"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("addEventListener")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v("'keypress'")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" checkName"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token boolean"}},[t._v("false")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("function")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("checkName")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token parameter"}},[t._v("e")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n  "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("if")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("e"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("charCode "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("<")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("97")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("||")]),t._v(" e"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("charCode "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v(">")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("122")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n    e"),s("span",{pre:!0,attrs:{class:"token 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"),s("div",{staticClass:"line-numbers-wrapper"},[s("span",{staticClass:"line-number"},[t._v("1")]),s("br"),s("span",{staticClass:"line-number"},[t._v("2")]),s("br"),s("span",{staticClass:"line-number"},[t._v("3")]),s("br"),s("span",{staticClass:"line-number"},[t._v("4")]),s("br"),s("span",{staticClass:"line-number"},[t._v("5")]),s("br"),s("span",{staticClass:"line-number"},[t._v("6")]),s("br"),s("span",{staticClass:"line-number"},[t._v("7")]),s("br"),s("span",{staticClass:"line-number"},[t._v("8")]),s("br"),s("span",{staticClass:"line-number"},[t._v("9")]),s("br"),s("span",{staticClass:"line-number"},[t._v("10")]),s("br")])]),s("p",[t._v("上面代码为文本框的"),s("code",[t._v("keypress")]),t._v("事件设定监听函数后，将只能输入小写字母，否则输入事件的默认行为（写入文本框）将被取消，导致不能向文本框输入内容。")]),t._v(" "),s("h4",{attrs:{id:"_3-2-event-stoppropagation-阻止事件传播"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_3-2-event-stoppropagation-阻止事件传播"}},[t._v("#")]),t._v(" 3.2 Event.stopPropagation() 阻止事件传播")]),t._v(" "),s("p",[s("code",[t._v("stopPropagation")]),t._v("方法阻止事件在 DOM 中继续传播，防止再触发定义在别的节点上的监听函数，但是不包括在当前节点上其他的事件监听函数。")]),t._v(" "),s("div",{staticClass:"language-js line-numbers-mode"},[s("pre",{pre:!0,attrs:{class:"language-js"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("function")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stopEvent")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token parameter"}},[t._v("e")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n  e"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stopPropagation")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// 阻止事件冒泡")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\nel"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("addEventListener")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v("'click'")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" stopEvent"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token boolean"}},[t._v("false")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n")])]),t._v(" "),s("div",{staticClass:"line-numbers-wrapper"},[s("span",{staticClass:"line-number"},[t._v("1")]),s("br"),s("span",{staticClass:"line-number"},[t._v("2")]),s("br"),s("span",{staticClass:"line-number"},[t._v("3")]),s("br"),s("span",{staticClass:"line-number"},[t._v("4")]),s("br"),s("span",{staticClass:"line-number"},[t._v("5")]),s("br")])]),s("p",[t._v("上面代码中，"),s("code",[t._v("click")]),t._v("事件将不会进一步冒泡到"),s("code",[t._v("el")]),t._v("节点的父节点。")]),t._v(" "),s("h4",{attrs:{id:"_3-3-event-stopimmediatepropagation-阻止同一个事件的其他监听函数被调用"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_3-3-event-stopimmediatepropagation-阻止同一个事件的其他监听函数被调用"}},[t._v("#")]),t._v(" 3.3 Event.stopImmediatePropagation() 阻止同一个事件的其他监听函数被调用")]),t._v(" "),s("p",[s("code",[t._v("Event.stopImmediatePropagation")]),t._v("方法阻止同一个事件的其他监听函数被调用，不管监听函数定义在当前节点还是其他节点。也就是说，该方法阻止事件的传播，比"),s("code",[t._v("Event.stopPropagation()")]),t._v("更彻底。")]),t._v(" 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"),s("div",{staticClass:"line-numbers-wrapper"},[s("span",{staticClass:"line-number"},[t._v("1")]),s("br"),s("span",{staticClass:"line-number"},[t._v("2")]),s("br"),s("span",{staticClass:"line-number"},[t._v("3")]),s("br"),s("span",{staticClass:"line-number"},[t._v("4")]),s("br"),s("span",{staticClass:"line-number"},[t._v("5")]),s("br"),s("span",{staticClass:"line-number"},[t._v("6")]),s("br"),s("span",{staticClass:"line-number"},[t._v("7")]),s("br"),s("span",{staticClass:"line-number"},[t._v("8")]),s("br"),s("span",{staticClass:"line-number"},[t._v("9")]),s("br"),s("span",{staticClass:"line-number"},[t._v("10")]),s("br")])]),s("p",[t._v("上面代码在"),s("code",[t._v("el")]),t._v("节点上，为"),s("code",[t._v("click")]),t._v("事件添加了两个监听函数"),s("code",[t._v("l1")]),t._v("和"),s("code",[t._v("l2")]),t._v("。由于"),s("code",[t._v("l1")]),t._v("调用了"),s("code",[t._v("event.stopImmediatePropagation")]),t._v("方法，所以"),s("code",[t._v("l2")]),t._v("不会被调用。")]),t._v(" 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"),s("div",{staticClass:"line-numbers-wrapper"},[s("span",{staticClass:"line-number"},[t._v("1")]),s("br"),s("span",{staticClass:"line-number"},[t._v("2")]),s("br"),s("span",{staticClass:"line-number"},[t._v("3")]),s("br"),s("span",{staticClass:"line-number"},[t._v("4")]),s("br"),s("span",{staticClass:"line-number"},[t._v("5")]),s("br"),s("span",{staticClass:"line-number"},[t._v("6")]),s("br"),s("span",{staticClass:"line-number"},[t._v("7")]),s("br"),s("span",{staticClass:"line-number"},[t._v("8")]),s("br"),s("span",{staticClass:"line-number"},[t._v("9")]),s("br"),s("span",{staticClass:"line-number"},[t._v("10")]),s("br"),s("span",{staticClass:"line-number"},[t._v("11")]),s("br")])]),s("p",[t._v("上面代码中，"),s("code",[t._v("click")]),t._v("事件的最底层节点是"),s("code",[t._v("p")]),t._v("，向上依次是"),s("code",[t._v("div")]),t._v("、"),s("code",[t._v("body")]),t._v("、"),s("code",[t._v("html")]),t._v("、"),s("code",[t._v("document")]),t._v("、"),s("code",[t._v("Window")]),t._v("。")]),t._v(" "),s("h2",{attrs:{id:"四、鼠标事件"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#四、鼠标事件"}},[t._v("#")]),t._v(" 四、鼠标事件")]),t._v(" "),s("h3",{attrs:{id:"_1、鼠标事件的种类"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_1、鼠标事件的种类"}},[t._v("#")]),t._v(" 1、鼠标事件的种类")]),t._v(" "),s("p",[t._v("鼠标事件指与鼠标相关的事件，继承了"),s("code",[t._v("MouseEvent")]),t._v("接口。具体的事件主要有以下一些。")]),t._v(" "),s("ul",[s("li",[s("code",[t._v("click")]),t._v("：按下鼠标（通常是按下主按钮）时触发。"),s("strong",[t._v("【单击】")])]),t._v(" "),s("li",[s("code",[t._v("dblclick")]),t._v("：在同一个元素上双击鼠标时触发。"),s("strong",[t._v("【双击】")])]),t._v(" "),s("li",[s("code",[t._v("mousedown")]),t._v("：按下鼠标键时触发。"),s("strong",[t._v("【按下】")])]),t._v(" "),s("li",[s("code",[t._v("mouseup")]),t._v("：释放按下的鼠标键时触发。"),s("strong",[t._v("【抬起】")])]),t._v(" "),s("li",[s("code",[t._v("mousemove")]),t._v("：当鼠标在一个节点内部移动时触发。当鼠标持续移动时，该事件会连续触发。为了避免性能问题，建议对该事件的监听函数做一些限定，比如限定一段时间内只能运行一次。"),s("strong",[t._v("【经过（多次）】")])]),t._v(" "),s("li",[s("code",[t._v("mouseenter")]),t._v("：鼠标进入一个节点时触发，进入子节点不会触发这个事件（详见后文）。"),s("strong",[t._v("【进入（单次）】")])]),t._v(" "),s("li",[s("code",[t._v("mouseover")]),t._v("：鼠标进入一个节点时触发，进入子节点会再一次触发这个事件（详见后文）。"),s("strong",[t._v("【进入+子节点】")])]),t._v(" "),s("li",[s("code",[t._v("mouseleave")]),t._v("：鼠标离开一个节点时触发，离开父节点不会触发这个事件（详见后文）。"),s("strong",[t._v("【离开（单次）】")])]),t._v(" "),s("li",[s("code",[t._v("mouseout")]),t._v("：鼠标离开一个节点时触发，离开父节点会触发这个事件（详见后文）。"),s("strong",[t._v("【离开+子节点】")])]),t._v(" "),s("li",[s("code",[t._v("contextmenu")]),t._v("：按下鼠标右键时（上下文菜单出现前）触发，或者按下“上下文菜单键”时触发。"),s("strong",[t._v("【右键】")])]),t._v(" "),s("li",[s("code",[t._v("wheel")]),t._v("：滚动鼠标的滚轮时触发，该事件继承的是"),s("code",[t._v("WheelEvent")]),t._v("接口。"),s("strong",[t._v("【滚轮】")])])]),t._v(" "),s("p",[s("code",[t._v("click")]),t._v("事件指的是，用户在同一个位置先完成"),s("code",[t._v("mousedown")]),t._v("动作，再完成"),s("code",[t._v("mouseup")]),t._v("动作。因此，触发顺序是，"),s("code",[t._v("mousedown")]),t._v("首先触发，"),s("code",[t._v("mouseup")]),t._v("接着触发，"),s("code",[t._v("click")]),t._v("最后触发。")]),t._v(" "),s("p",[s("code",[t._v("dblclick")]),t._v("事件则会在"),s("code",[t._v("mousedown")]),t._v("、"),s("code",[t._v("mouseup")]),t._v("、"),s("code",[t._v("click")]),t._v("之后触发。")]),t._v(" "),s("p",[s("code",[t._v("mouseover")]),t._v("事件和"),s("code",[t._v("mouseenter")]),t._v("事件，都是鼠标进入一个节点时触发。两者的区别是，"),s("code",[t._v("mouseenter")]),t._v("事件只触发一次，而只要鼠标在节点内部移动，"),s("code",[t._v("mouseover")]),t._v("事件会在子节点上触发多次。")]),t._v(" "),s("div",{staticClass:"language-js line-numbers-mode"},[s("pre",{pre:!0,attrs:{class:"language-js"}},[s("code",[s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("/* HTML 代码如下\n <ul>\n   <li>item 1</li>\n   <li>item 2</li>\n  <li>item 3</li>\n 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"),s("h4",{attrs:{id:"_5-1-概述"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_5-1-概述"}},[t._v("#")]),t._v(" 5.1 概述")]),t._v(" "),s("p",[s("strong",[t._v("WheelEvent 接口继承了 MouseEvent 实例，代表鼠标滚轮事件的实例对象")]),t._v("。目前，鼠标滚轮相关的事件只有一个"),s("code",[t._v("wheel")]),t._v("事件，用户滚动鼠标的滚轮，就生成这个事件的实例。")]),t._v(" "),s("p",[t._v("浏览器原生提供"),s("code",[t._v("WheelEvent()")]),t._v("构造函数，用来生成"),s("code",[t._v("WheelEvent")]),t._v("实例。")]),t._v(" "),s("div",{staticClass:"language-js line-numbers-mode"},[s("pre",{pre:!0,attrs:{class:"language-js"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("var")]),t._v(" wheelEvent "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("WheelEvent")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("type"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" 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"),s("li",[s("code",[t._v("deltaMode")]),t._v("：数值，表示相关的滚动事件的单位，适用于上面三个属性。"),s("code",[t._v("0")]),t._v("表示滚动单位为像素，"),s("code",[t._v("1")]),t._v("表示单位为行，"),s("code",[t._v("2")]),t._v("表示单位为页，默认为"),s("code",[t._v("0")]),t._v("。")])]),t._v(" "),s("h4",{attrs:{id:"_5-2-实例属性"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_5-2-实例属性"}},[t._v("#")]),t._v(" 5.2 实例属性")]),t._v(" "),s("p",[s("code",[t._v("WheelEvent")]),t._v("事件实例除了具有"),s("code",[t._v("Event")]),t._v("和"),s("code",[t._v("MouseEvent")]),t._v("的实例属性和实例方法，还有一些自己的实例属性，但是没有自己的实例方法。")]),t._v(" "),s("p",[t._v("下面的属性都是只读属性。")]),t._v(" "),s("ul",[s("li",[s("code",[t._v("WheelEvent.deltaX")]),t._v("：数值，表示滚轮的水平滚动量。")]),t._v(" "),s("li",[s("code",[t._v("WheelEvent.deltaY")]),t._v("：数值，表示滚轮的垂直滚动量。")]),t._v(" "),s("li",[s("code",[t._v("WheelEvent.deltaZ")]),t._v("：数值，表示滚轮的 Z 轴滚动量。")]),t._v(" "),s("li",[s("code",[t._v("WheelEvent.deltaMode")]),t._v("：数值，表示上面三个属性的单位，"),s("code",[t._v("0")]),t._v("是像素，"),s("code",[t._v("1")]),t._v("是行，"),s("code",[t._v("2")]),t._v("是页。")])]),t._v(" "),s("h2",{attrs:{id:"五、键盘事件"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#五、键盘事件"}},[t._v("#")]),t._v(" 五、键盘事件")]),t._v(" "),s("h3",{attrs:{id:"_1、键盘事件的种类"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_1、键盘事件的种类"}},[t._v("#")]),t._v(" 1、键盘事件的种类")]),t._v(" "),s("p",[t._v("键盘事件由用户击打键盘触发，主要有"),s("code",[t._v("keydown")]),t._v("、"),s("code",[t._v("keypress")]),t._v("、"),s("code",[t._v("keyup")]),t._v("三个事件，它们都继承了"),s("code",[t._v("KeyboardEvent")]),t._v("接口。")]),t._v(" "),s("ul",[s("li",[s("code",[t._v("keydown")]),t._v("：按下键盘时触发。"),s("strong",[t._v("【按下】")])]),t._v(" "),s("li",[s("code",[t._v("keypress")]),t._v("：按下有值的键时触发，即按下 Ctrl、Alt、Shift、Meta 这样无值的键，这个事件不会触发。对于有值的键，按下时先触发"),s("code",[t._v("keydown")]),t._v("事件，再触发这个事件。"),s("strong",[t._v("【按下有值的键】")])]),t._v(" "),s("li",[s("code",[t._v("keyup")]),t._v("：松开键盘时触发该事件。"),s("strong",[t._v("【松开】")])])]),t._v(" "),s("p",[t._v("如果用户一直按键不松开，就会连续触发键盘事件，触发的顺序如下。")]),t._v(" "),s("ol",[s("li",[t._v("keydown")]),t._v(" "),s("li",[t._v("keypress")]),t._v(" "),s("li",[t._v("keydown")]),t._v(" "),s("li",[t._v("keypress")]),t._v(" "),s("li",[t._v("...（重复以上过程）")]),t._v(" "),s("li",[t._v("keyup")])]),t._v(" "),s("h3",{attrs:{id:"_2、keyboardevent-接口概述"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_2、keyboardevent-接口概述"}},[t._v("#")]),t._v(" 2、KeyboardEvent 接口概述")]),t._v(" "),s("p",[s("code",[t._v("KeyboardEvent")]),t._v("接口用来描述用户与键盘的互动。这个接口"),s("strong",[t._v("继承了"),s("code",[t._v("Event")]),t._v("接口")]),t._v("，并且定义了自己的实例属性和实例方法。")]),t._v(" "),s("p",[t._v("浏览器原生提供"),s("code",[t._v("KeyboardEvent")]),t._v("构造函数，用来新建键盘事件的实例。")]),t._v(" "),s("div",{staticClass:"language-js line-numbers-mode"},[s("pre",{pre:!0,attrs:{class:"language-js"}},[s("code",[s("span",{pre:!0,attrs:{class:"token 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"),s("li",[s("code",[t._v("code")]),t._v("：字符串，表示当前按下的键的字符串形式，默认为空字符串。"),s("strong",[t._v("【键码】")])]),t._v(" "),s("li",[s("code",[t._v("location")]),t._v("：整数，当前按下的键的位置，默认为"),s("code",[t._v("0")]),t._v("。")]),t._v(" "),s("li",[s("code",[t._v("ctrlKey")]),t._v("：布尔值，是否按下 Ctrl 键，默认为"),s("code",[t._v("false")]),t._v("。")]),t._v(" "),s("li",[s("code",[t._v("shiftKey")]),t._v("：布尔值，是否按下 Shift 键，默认为"),s("code",[t._v("false")]),t._v("。")]),t._v(" "),s("li",[s("code",[t._v("altKey")]),t._v("：布尔值，是否按下 Alt 键，默认为"),s("code",[t._v("false")]),t._v("。")]),t._v(" "),s("li",[s("code",[t._v("metaKey")]),t._v("：布尔值，是否按下 Meta 键，默认为"),s("code",[t._v("false")]),t._v("。")]),t._v(" "),s("li",[s("code",[t._v("repeat")]),t._v("：布尔值，是否重复按键，默认为"),s("code",[t._v("false")]),t._v("。")])]),t._v(" "),s("h3",{attrs:{id:"_3、keyboardevent-的实例属性"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_3、keyboardevent-的实例属性"}},[t._v("#")]),t._v(" 3、KeyboardEvent 的实例属性")]),t._v(" "),s("h4",{attrs:{id:"_3-1-keyboardevent-altkey-keyboardevent-ctrlkey-keyboardevent-metakey-keyboardevent-shiftkey-【是否按下对应键-布尔值】"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_3-1-keyboardevent-altkey-keyboardevent-ctrlkey-keyboardevent-metakey-keyboardevent-shiftkey-【是否按下对应键-布尔值】"}},[t._v("#")]),t._v(" 3.1 KeyboardEvent.altKey，KeyboardEvent.ctrlKey，KeyboardEvent.metaKey，KeyboardEvent.shiftKey 【是否按下对应键，布尔值】")]),t._v(" "),s("p",[t._v("以下属性都是"),s("strong",[t._v("只读")]),t._v("属性，返回一个布尔值，表示是否按下对应的键。")]),t._v(" "),s("ul",[s("li",[s("code",[t._v("KeyboardEvent.altKey")]),t._v("：是否按下 Alt 键")]),t._v(" "),s("li",[s("code",[t._v("KeyboardEvent.ctrlKey")]),t._v("：是否按下 Ctrl 键")]),t._v(" "),s("li",[s("code",[t._v("KeyboardEvent.metaKey")]),t._v("：是否按下 meta 键（Mac 系统是一个四瓣的小花，Windows 系统是 windows 键）")]),t._v(" "),s("li",[s("code",[t._v("KeyboardEvent.shiftKey")]),t._v("：是否按下 Shift 键")])]),t._v(" "),s("p",[t._v("下面是一个示例。")]),t._v(" "),s("div",{staticClass:"language-js line-numbers-mode"},[s("pre",{pre:!0,attrs:{class:"language-js"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("function")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("showChar")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token parameter"}},[t._v("e")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n  console"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("log")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v("'ALT: '")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("+")]),t._v(" e"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("altKey"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n  console"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("log")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v("'CTRL: '")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("+")]),t._v(" e"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("ctrlKey"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n  console"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("log")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v("'Meta: '")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("+")]),t._v(" e"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("metaKey"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n  console"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("log")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v("'Shift: '")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("+")]),t._v(" e"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("shiftKey"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\ndocument"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("body"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("addEventListener")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v("'keydown'")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" showChar"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token boolean"}},[t._v("false")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n")])]),t._v(" "),s("div",{staticClass:"line-numbers-wrapper"},[s("span",{staticClass:"line-number"},[t._v("1")]),s("br"),s("span",{staticClass:"line-number"},[t._v("2")]),s("br"),s("span",{staticClass:"line-number"},[t._v("3")]),s("br"),s("span",{staticClass:"line-number"},[t._v("4")]),s("br"),s("span",{staticClass:"line-number"},[t._v("5")]),s("br"),s("span",{staticClass:"line-number"},[t._v("6")]),s("br"),s("span",{staticClass:"line-number"},[t._v("7")]),s("br"),s("span",{staticClass:"line-number"},[t._v("8")]),s("br")])]),s("h4",{attrs:{id:"_3-2-keyboardevent-code-键码"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_3-2-keyboardevent-code-键码"}},[t._v("#")]),t._v(" 3.2 KeyboardEvent.code 键码")]),t._v(" "),s("p",[s("code",[t._v("KeyboardEvent.code")]),t._v("属性"),s("strong",[t._v("返回一个字符串，表示当前按下的键的字符串形式")]),t._v("。该属性"),s("strong",[t._v("只读")]),t._v("。")]),t._v(" "),s("p",[t._v("下面是一些常用键的字符串形式，其他键请查"),s("a",{attrs:{href:"https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent/code#Code_values",target:"_blank",rel:"noopener noreferrer"}},[t._v("文档"),s("OutboundLink")],1),t._v("。")]),t._v(" "),s("ul",[s("li",[t._v("数字键0 - 9：返回"),s("code",[t._v("digital0")]),t._v(" - "),s("code",[t._v("digital9")])]),t._v(" "),s("li",[t._v("字母键A - z：返回"),s("code",[t._v("KeyA")]),t._v(" - "),s("code",[t._v("KeyZ")])]),t._v(" "),s("li",[t._v("功能键F1 - F12：返回 "),s("code",[t._v("F1")]),t._v(" - "),s("code",[t._v("F12")])]),t._v(" "),s("li",[t._v("方向键：返回"),s("code",[t._v("ArrowDown")]),t._v("、"),s("code",[t._v("ArrowUp")]),t._v("、"),s("code",[t._v("ArrowLeft")]),t._v("、"),s("code",[t._v("ArrowRight")])]),t._v(" "),s("li",[t._v("Alt 键：返回"),s("code",[t._v("AltLeft")]),t._v("或"),s("code",[t._v("AltRight")])]),t._v(" "),s("li",[t._v("Shift 键：返回"),s("code",[t._v("ShiftLeft")]),t._v("或"),s("code",[t._v("ShiftRight")])]),t._v(" "),s("li",[t._v("Ctrl 键：返回"),s("code",[t._v("ControlLeft")]),t._v("或"),s("code",[t._v("ControlRight")])])]),t._v(" "),s("h4",{attrs:{id:"_3-3-keyboardevent-key-键名"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_3-3-keyboardevent-key-键名"}},[t._v("#")]),t._v(" 3.3 KeyboardEvent.key 键名")]),t._v(" "),s("p",[s("code",[t._v("KeyboardEvent.key")]),t._v("属性"),s("strong",[t._v("返回一个字符串，表示按下的键名")]),t._v("。该属性"),s("strong",[t._v("只读")]),t._v("。")]),t._v(" "),s("p",[t._v("如果按下的键代表可打印字符，则返回这个字符，比如数字、字母。")]),t._v(" "),s("p",[t._v("如果按下的键代表不可打印的特殊字符，则返回预定义的键值，比如 Backspace，Tab，Enter，Shift，Control，Alt，CapsLock，Esc，Spacebar，PageUp，PageDown，End，Home，Left，Right，Up，Down，PrintScreen，Insert，Del，Win，F1～F12，NumLock，Scroll 等。")]),t._v(" "),s("p",[t._v("如果同时按下一个控制键和一个符号键，则返回符号键的键名。比如，按下 Ctrl + a，则返回"),s("code",[t._v("a")]),t._v("；按下 Shift + a，则返回大写的"),s("code",[t._v("A")]),t._v("。")]),t._v(" "),s("p",[t._v("如果无法识别键名，返回字符串"),s("code",[t._v("Unidentified")]),t._v("。")]),t._v(" "),s("h4",{attrs:{id:"_3-4-keyboardevent-location-键处于哪个位置-整数"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_3-4-keyboardevent-location-键处于哪个位置-整数"}},[t._v("#")]),t._v(" 3.4 KeyboardEvent.location 键处于哪个位置，整数")]),t._v(" "),s("p",[s("code",[t._v("KeyboardEvent.location")]),t._v("属性"),s("strong",[t._v("返回一个整数，表示按下的键处在键盘的哪一个区域")]),t._v("。它可能取以下值。")]),t._v(" "),s("ul",[s("li",[s("p",[t._v("0：处在键盘的主区域，或者无法判断处于哪一个区域。")])]),t._v(" "),s("li",[s("p",[t._v("1：处在键盘的左侧，只适用那些有两个位置的键（比如 Ctrl 和 Shift 键）。")])]),t._v(" "),s("li",[s("p",[t._v("2：处在键盘的右侧，只适用那些有两个位置的键（比如 Ctrl 和 Shift 键）。")])]),t._v(" "),s("li",[s("p",[t._v("3：处在数字小键盘。")])])]),t._v(" "),s("h4",{attrs:{id:"_3-5-keyboardevent-repeat-是否长按"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_3-5-keyboardevent-repeat-是否长按"}},[t._v("#")]),t._v(" 3.5 KeyboardEvent.repeat 是否长按")]),t._v(" "),s("p",[s("code",[t._v("KeyboardEvent.repeat")]),t._v("返回一个"),s("strong",[t._v("布尔值，代表该键是否被按着不放")]),t._v("，以便判断是否重复这个键，即浏览器会持续触发"),s("code",[t._v("keydown")]),t._v("和"),s("code",[t._v("keypress")]),t._v("事件，直到用户松开手为止。")]),t._v(" "),s("h3",{attrs:{id:"_4、keyboardevent-的实例方法"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_4、keyboardevent-的实例方法"}},[t._v("#")]),t._v(" 4、KeyboardEvent 的实例方法")]),t._v(" "),s("h4",{attrs:{id:"_4-1-keyboardevent-getmodifierstate-是否按下指定功能键"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_4-1-keyboardevent-getmodifierstate-是否按下指定功能键"}},[t._v("#")]),t._v(" 4.1 KeyboardEvent.getModifierState() 是否按下指定功能键")]),t._v(" "),s("p",[s("code",[t._v("KeyboardEvent.getModifierState()")]),t._v("方法返回一个"),s("strong",[t._v("布尔值，表示是否按下或激活指定的功能键")]),t._v("。它的常用参数如下。")]),t._v(" "),s("ul",[s("li",[s("code",[t._v("Alt")]),t._v("：Alt 键")]),t._v(" "),s("li",[s("code",[t._v("CapsLock")]),t._v("：大写锁定键")]),t._v(" "),s("li",[s("code",[t._v("Control")]),t._v("：Ctrl 键")]),t._v(" "),s("li",[s("code",[t._v("Meta")]),t._v("：Meta 键")]),t._v(" "),s("li",[s("code",[t._v("NumLock")]),t._v("：数字键盘开关键")]),t._v(" "),s("li",[s("code",[t._v("Shift")]),t._v("：Shift 键")])]),t._v(" "),s("div",{staticClass:"language-js line-numbers-mode"},[s("pre",{pre:!0,attrs:{class:"language-js"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("if")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("\n  event"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("getModifierState")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v("'Control'")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("+")]),t._v("\n  event"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token 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"),s("p",[s("code",[t._v("Touch.clientX")]),t._v("属性和"),s("code",[t._v("Touch.clientY")]),t._v("属性，分别表示触摸点相对于浏览器视口左上角的横坐标和纵坐标，与页面是否滚动无关。")]),t._v(" "),s("p",[s("code",[t._v("Touch.pageX")]),t._v("属性和"),s("code",[t._v("Touch.pageY")]),t._v("属性，分别表示触摸点相对于当前页面左上角的横坐标和纵坐标，包含了页面滚动带来的位移。")]),t._v(" "),s("h5",{attrs:{id:"_3-touch-radiusx-touch-radiusy-touch-rotationangle-触摸椭圆区域半径、角度"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_3-touch-radiusx-touch-radiusy-touch-rotationangle-触摸椭圆区域半径、角度"}},[t._v("#")]),t._v(" （3）Touch.radiusX，Touch.radiusY，Touch.rotationAngle （触摸椭圆区域半径、角度）")]),t._v(" "),s("p",[s("code",[t._v("Touch.radiusX")]),t._v("属性和"),s("code",[t._v("Touch.radiusY")]),t._v("属性，分别返回"),s("strong",[t._v("触摸点周围受到影响的椭圆范围的 X 轴半径和 Y 轴半径，单位为像素。乘以 2 就可以得到触摸范围的宽度和高度")]),t._v("。")]),t._v(" "),s("p",[s("code",[t._v("Touch.rotationAngle")]),t._v("属性表示触摸区域的椭圆的旋转角度，单位为度数，在"),s("code",[t._v("0")]),t._v("到"),s("code",[t._v("90")]),t._v("度之间。")]),t._v(" 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"),s("p",[s("code",[t._v("Touch.force")]),t._v("属性返回一个"),s("code",[t._v("0")]),t._v("到"),s("code",[t._v("1")]),t._v("之间的数值，表示触摸压力。"),s("code",[t._v("0")]),t._v("代表没有压力，"),s("code",[t._v("1")]),t._v("代表硬件所能识别的最大压力。")]),t._v(" "),s("h5",{attrs:{id:"_5-touch-target-开始触摸时的元素"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_5-touch-target-开始触摸时的元素"}},[t._v("#")]),t._v(" （5）Touch.target 开始触摸时的元素")]),t._v(" "),s("p",[s("code",[t._v("Touch.target")]),t._v("属性返回一个元素节点，代表触摸发生时所在的那个元素节点。即使触摸点已经离开了这个节点，该属性依然不变。")]),t._v(" "),s("h3",{attrs:{id:"_3、touchlist-接口"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_3、touchlist-接口"}},[t._v("#")]),t._v(" 3、TouchList 接口")]),t._v(" "),s("p",[s("code",[t._v("TouchList")]),t._v("接口"),s("strong",[t._v("表示一组触摸点的集合")]),t._v("。它的实例是一个"),s("strong",[t._v("类似数组的对象")]),t._v("，成员是"),s("code",[t._v("Touch")]),t._v("的实例对象，表示所有触摸点。用户用三根手指触摸，产生的"),s("code",[t._v("TouchList")]),t._v("实例就会包含三个成员，每根手指的触摸点对应一个"),s("code",[t._v("Touch")]),t._v("实例对象。")]),t._v(" "),s("p",[t._v("它的实例主要通过触摸事件的"),s("code",[t._v("TouchEvent.touches")]),t._v("、"),s("code",[t._v("TouchEvent.changedTouches")]),t._v("、"),s("code",[t._v("TouchEvent.targetTouches")]),t._v("这几个属性获取。")]),t._v(" "),s("p",[t._v("它的实例属性和实例方法只有两个。")]),t._v(" "),s("ul",[s("li",[s("code",[t._v("TouchList.length")]),t._v("：数值，表示成员数量（即触摸点的数量）。")]),t._v(" "),s("li",[s("code",[t._v("TouchList.item()")]),t._v("：返回指定位置的成员，它的参数是该成员的位置编号（从零开始）。")])]),t._v(" "),s("h3",{attrs:{id:"_4、touchevent-接口"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_4、touchevent-接口"}},[t._v("#")]),t._v(" 4、TouchEvent 接口")]),t._v(" "),s("h4",{attrs:{id:"_4-1-概述"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_4-1-概述"}},[t._v("#")]),t._v(" 4.1 概述")]),t._v(" "),s("p",[t._v("TouchEvent 接口"),s("strong",[t._v("继承了 Event 接口")]),t._v("，表示由"),s("strong",[t._v("触摸引发的事件实例")]),t._v("，通常来自触摸屏或轨迹板。除了被继承的属性以外，它还有一些自己的属性。")]),t._v(" "),s("p",[t._v("浏览器原生提供"),s("code",[t._v("TouchEvent()")]),t._v("构造函数，用来生成触摸事件的实例。")]),t._v(" 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"),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// 将被拖拉节点插入目标节点")]),t._v("\n    dragged"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("parentNode"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("removeChild")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("dragged"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n    event"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("target"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("appendChild")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v(" dragged "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n  "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token boolean"}},[t._v("false")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n")])]),t._v(" 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"),s("ul",[s("li",[t._v("拖拉过程只触发以上这些拖拉事件，尽管鼠标在移动，但是"),s("strong",[t._v("鼠标事件不会触发")]),t._v("。")]),t._v(" "),s("li",[t._v("将文件从操作系统拖拉进浏览器，不会触发"),s("code",[t._v("dragstart")]),t._v("和"),s("code",[t._v("dragend")]),t._v("事件。")]),t._v(" "),s("li",[s("code",[t._v("dragenter")]),t._v("和"),s("code",[t._v("dragover")]),t._v("事件的监听函数，用来取出拖拉的数据（即允许放下被拖拉的元素）。由于网页的大部分区域不适合作为放下拖拉元素的目标节点，所以这两个事件的默认设置为当前节点不允许接受被拖拉的元素。"),s("strong",[t._v("如果想要在目标节点上放下的数据，首先必须阻止这两个事件的默认行为")]),t._v("。")])]),t._v(" "),s("div",{staticClass:"language-html line-numbers-mode"},[s("pre",{pre:!0,attrs:{class:"language-html"}},[s("code",[s("span",{pre:!0,attrs:{class:"token tag"}},[s("span",{pre:!0,attrs:{class:"token tag"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),t._v("div")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token attr-name"}},[t._v("ondragover")]),s("span",{pre:!0,attrs:{class:"token attr-value"}},[s("span",{pre:!0,attrs:{class:"token punctuation 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"),s("div",{staticClass:"line-numbers-wrapper"},[s("span",{staticClass:"line-number"},[t._v("1")]),s("br"),s("span",{staticClass:"line-number"},[t._v("2")]),s("br")])]),s("p",[t._v("上面代码中，如果不取消拖拉事件或者阻止默认行为，就不能在"),s("code",[t._v("div")]),t._v("节点上放下被拖拉的节点。")]),t._v(" "),s("h3",{attrs:{id:"_2、dragevent-接口"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_2、dragevent-接口"}},[t._v("#")]),t._v(" 2、DragEvent 接口")]),t._v(" "),s("p",[s("strong",[t._v("拖拉事件都继承了"),s("code",[t._v("DragEvent")]),t._v("接口，这个接口又继承了"),s("code",[t._v("MouseEvent")]),t._v("接口和"),s("code",[t._v("Event")]),t._v("接口。")])]),t._v(" "),s("p",[t._v("浏览器原生提供一个"),s("code",[t._v("DragEvent()")]),t._v("构造函数，用来生成拖拉事件的实例对象。")]),t._v(" "),s("div",{staticClass:"language-js line-numbers-mode"},[s("pre",{pre:!0,attrs:{class:"language-js"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("DragEvent")]),s("span",{pre:!0,attrs:{class:"token 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"),s("h3",{attrs:{id:"_3、datatransfer-接口概述"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_3、datatransfer-接口概述"}},[t._v("#")]),t._v(" 3、DataTransfer 接口概述")]),t._v(" "),s("p",[s("strong",[t._v("所有拖拉事件的实例都有一个"),s("code",[t._v("DragEvent.dataTransfer")]),t._v("属性，用来读写需要传递的数据")]),t._v("。这个属性的值是一个"),s("code",[t._v("DataTransfer")]),t._v("接口的实例。")]),t._v(" "),s("p",[t._v("浏览器原生提供一个"),s("code",[t._v("DataTransfer()")]),t._v("构造函数，用来生成"),s("code",[t._v("DataTransfer")]),t._v("实例对象。")]),t._v(" "),s("div",{staticClass:"language-js line-numbers-mode"},[s("pre",{pre:!0,attrs:{class:"language-js"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("var")]),t._v(" dataTrans "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("DataTransfer")]),s("span",{pre:!0,attrs:{class:"token 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"),s("h3",{attrs:{id:"_4、datatransfer-的实例属性"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_4、datatransfer-的实例属性"}},[t._v("#")]),t._v(" 4、DataTransfer 的实例属性")]),t._v(" "),s("h4",{attrs:{id:"_4-1-datatransfer-dropeffect-设置接受拖拉的区域的效果"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_4-1-datatransfer-dropeffect-设置接受拖拉的区域的效果"}},[t._v("#")]),t._v(" 4.1 DataTransfer.dropEffect 设置接受拖拉的区域的效果")]),t._v(" "),s("p",[s("code",[t._v("DataTransfer.dropEffect")]),t._v("属性"),s("strong",[t._v("用来设置放下（drop）被拖拉节点时的效果")]),t._v("，会影响到拖拉经过相关区域时鼠标的形状。它可能取下面的值。")]),t._v(" "),s("ul",[s("li",[t._v("copy：复制被拖拉的节点")]),t._v(" "),s("li",[t._v("move：移动被拖拉的节点")]),t._v(" "),s("li",[t._v("link：创建指向被拖拉的节点的链接")]),t._v(" "),s("li",[t._v("none：无法放下被拖拉的节点")])]),t._v(" "),s("p",[t._v("除了上面这些值，设置其他的值都是无效的。")]),t._v(" "),s("div",{staticClass:"language-js line-numbers-mode"},[s("pre",{pre:!0,attrs:{class:"language-js"}},[s("code",[t._v("target"),s("span",{pre:!0,attrs:{class:"token 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"),s("p",[t._v("注意，该方法"),s("strong",[t._v("只能在"),s("code",[t._v("dragstart")]),t._v("事件的监听函数之中使用")]),t._v("，因为这是拖拉操作的数据唯一可写的时机。")]),t._v(" "),s("h4",{attrs:{id:"_5-4-datatransfer-setdragimage-设置拖动过程中的图片"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_5-4-datatransfer-setdragimage-设置拖动过程中的图片"}},[t._v("#")]),t._v(" 5.4 DataTransfer.setDragImage() 设置拖动过程中的图片")]),t._v(" "),s("p",[t._v("拖动过程中（"),s("code",[t._v("dragstart")]),t._v("事件触发后），浏览器"),s("strong",[t._v("会显示一张图片跟随鼠标一起移动")]),t._v("，表示被拖动的节点。这张图片是"),s("strong",[t._v("自动创造的")]),t._v("，通常显示为被拖动节点的外观，不需要自己动手设置。")]),t._v(" "),s("p",[s("code",[t._v("DataTransfer.setDragImage()")]),t._v("方法"),s("strong",[t._v("可以自定义这张图片")]),t._v("。它接受三个参数。第一个是"),s("code",[t._v("<img>")]),t._v("节点或者"),s("code",[t._v("<canvas>")]),t._v("节点，如果省略或为"),s("code",[t._v("null")]),t._v("，则使用被拖动的节点的外观；第二个和第三个参数为鼠标相对于该图片左上角的横坐标和右坐标。")]),t._v(" "),s("p",[t._v("下面是一个例子。")]),t._v(" "),s("div",{staticClass:"language-js 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1、资源事件")]),t._v(" "),s("h4",{attrs:{id:"_1-1-beforeunload-事件-关闭窗口前调用"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_1-1-beforeunload-事件-关闭窗口前调用"}},[t._v("#")]),t._v(" 1.1 beforeunload 事件 （关闭窗口前调用）")]),t._v(" "),s("p",[s("code",[t._v("beforeunload")]),t._v("事件在"),s("strong",[t._v("窗口、文档、各种资源将要卸载前触发")]),t._v("。它可以用来防止用户不小心卸载资源。")]),t._v(" "),s("p",[t._v("如果该事件对象的"),s("code",[t._v("returnValue")]),t._v("属性是一个非空字符串，那么浏览器就会弹出一个对话框，询问用户是否要卸载该资源。但是，用户指定的字符串可能无法显示，浏览器会展示预定义的字符串。如果用户点击“取消”按钮，资源就不会卸载。")]),t._v(" "),s("div",{staticClass:"language-js line-numbers-mode"},[s("pre",{pre:!0,attrs:{class:"language-js"}},[s("code",[t._v("window"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("addEventListener")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v("'beforeunload'")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" 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"),s("div",{staticClass:"line-numbers-wrapper"},[s("span",{staticClass:"line-number"},[t._v("1")]),s("br"),s("span",{staticClass:"line-number"},[t._v("2")]),s("br"),s("span",{staticClass:"line-number"},[t._v("3")]),s("br")])]),s("p",[t._v("上面代码中，用户如果"),s("strong",[t._v("关闭窗口，浏览器会弹出一个窗口，要求用户确认")]),t._v("。")]),t._v(" "),s("p",[t._v("浏览器对这个事件的行为很不一致，有的浏览器调用"),s("code",[t._v("event.preventDefault()")]),t._v("，也会弹出对话框。IE 浏览器需要显式返回一个非空的字符串，才会弹出对话框。而且，"),s("strong",[t._v("大多数浏览器在对话框中不显示指定文本，只显示默认文本")]),t._v("。因此，可以采用下面的写法，取得最大的兼容性。")]),t._v(" "),s("div",{staticClass:"language-js line-numbers-mode"},[s("pre",{pre:!0,attrs:{class:"language-js"}},[s("code",[t._v("window"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("addEventListener")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v("'beforeunload'")]),s("span",{pre:!0,attrs:{class:"token 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"),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("return")]),t._v(" confirmationMessage"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n")])]),t._v(" "),s("div",{staticClass:"line-numbers-wrapper"},[s("span",{staticClass:"line-number"},[t._v("1")]),s("br"),s("span",{staticClass:"line-number"},[t._v("2")]),s("br"),s("span",{staticClass:"line-number"},[t._v("3")]),s("br"),s("span",{staticClass:"line-number"},[t._v("4")]),s("br"),s("span",{staticClass:"line-number"},[t._v("5")]),s("br"),s("span",{staticClass:"line-number"},[t._v("6")]),s("br")])]),s("p",[t._v("注意，许多手机浏览器默认忽略这个事件，桌面浏览器也有办法忽略这个事件。所以，它可能根本不会生效，不能依赖它来阻止用户关闭窗口。另外，一旦使用了"),s("code",[t._v("beforeunload")]),t._v("事件，浏览器就不会缓存当前网页，使用“回退”按钮将重新向服务器请求网页。这是因为监听这个事件的目的，一般是修改初始状态，这时缓存初始页面就没意义了。")]),t._v(" "),s("p",[t._v("基本上，只有一种场合可以监听"),s("code",[t._v("unload")]),t._v("事件，其他情况都不应该监听："),s("strong",[t._v("用户修改了表单，还没有保存就要离开")]),t._v("。")]),t._v(" "),s("h4",{attrs:{id:"_1-2-unload-事件-即将关闭窗口时调用"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#_1-2-unload-事件-即将关闭窗口时调用"}},[t._v("#")]),t._v(" 1.2 unload 事件 （即将关闭窗口时调用）")]),t._v(" "),s("p",[s("code",[t._v("unload")]),t._v("事件在"),s("strong",[t._v("窗口关闭或者"),s("code",[t._v("document")]),t._v("对象将要卸载时触发")]),t._v("。它的触发顺序排在"),s("code",[t._v("beforeunload")]),t._v("、"),s("code",[t._v("pagehide")]),t._v("事件后面。")]),t._v(" "),s("p",[s("code",[t._v("unload")]),t._v("事件发生时，文档处于一个特殊状态。所有资源依然存在，但是对用户来说都不可见，UI 互动全部无效。这个事件是无法取消的，即使在监听函数里面抛出错误，也不能停止文档的卸载。")]),t._v(" "),s("div",{staticClass:"language-js line-numbers-mode"},[s("pre",{pre:!0,attrs:{class:"language-js"}},[s("code",[t._v("window"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("addEventListener")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v("'unload'")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("function")]),s("span",{pre:!0,attrs:{class:"token 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